The social networking company says its new messaging system is one of the largest engineering projects Facebook has undertaken yet.

"We completely built the infrastructure [of the messaging system] with our biggest engineering team yet" said Facebook software engineer Andrew Bosworth at a press event Monday announcing the new service.

Facebook engineers still managed to figure out a way to give its more than 500 million users an @facebook.com email address, that will tie in Facebook's messaging system with SMS, IMs, email, and chat messages.